The one time that we were unable to get through to our DS5 and that he was "beyond our control" (not sure how else to say it) was last summer when he got a small cut on his hand.  He was so overcome by his concern and fear that he flat out refused to do anything we asked of him with respect to opening his hand to wash it.  It became a very bad scene with lots of upset from everyone.  In the immediate aftermath, I clued in to the fact that there was something so upsetting to him about the cut that he lost his ability to control the upset.  We didn't like the way we responded to it as parents, so we sought help.  We took our son to two sessions with a psychologist, which was preceded by one session with the psychologist just for us.  I also read the Explosive Child and lots of materials on the internet.  I turned to another online discussion group and tried to figure out how we could handle similar situations if they were ever to arise again.  I learned a great deal about our son and about our parenting style.  I regret that we had to go through an ugly night or two before I clued in but I am so thankful that there are resources in the community and online that are there to help.
DS5 had another fall and scrape in the schoolyard this year, which bled as well.  He does not like to bleed because he feels like he is "not himself"/ "not whole".  He was upset about it again this year and didn't deal with it perfectly, but with what we learned last year and with the extra year of maturity we were able to handle it with minimal upset.  Just yesterday he asked me to look at his knee and see that the scrape had gone away!  He said it was only in his brain now, as a memory.  We had also recently bought and read the book "Your Fantastic Elastic Brain" and we talked a lot about how he had stretched his amygdala, which was kind of fun.  
It seems that there is always something to learn on this parenting journey.  I sometimes feel like I am overreacting to everything and too quick to look for help rather than simply relying on my gut instinct.  However, the incident with the cut last summer brought to my attention very quickly that my own toolbox was not equipped to deal with his very unexpected reaction to a minor injury.  
I guess the point to my long-winded response is that there are lots of resources out there to help, although to be fair some of it is more easily accessible if you are able to pay for it out of pocket.  
I would add that I really wondered about the appropriateness of taking DS5 to a psychologist for help.  It is not something I had ever done before for myself or anyone else in my family.  I really puzzled it through and realized that my concern was actually coming from the stigmatization of mental health issues.  In the end I concluded that letting our son know that there is help in the community for mental health concerns is an important message to send.  
I'm not sure how applicable any of that is to your situation, though, since as you say I don't know your DS6.  We only have one child, so we don't have to deal with the interaction between brothers.  Our son does sometimes get silly about things, as does every child.  If he was ever to throw anything at us, or strike out, we would be quick to correct that sort of thing.  He is expected to think about other people around him and how his behaviour affects them on a daily basis.
Last edited by HJA; 06/15/16 09:12 AM.